Inlet manifolds

ABSTRACT

An inlet manifold for a multi-cylinder internal combustion engine comprises a plenum chamber which has an inlet containing at least one throttle valve and which has a plurality of outlet ducts each adapted to communicate with a respective cylinder of the engine via an inlet valve of the engine. A further valve is associated with each outlet duct which, in use, operates to control the flow of gas through that outlet duct under at least part of the range of operation of the throttle valve which controls the operation of the engine. The further valves may be respectively located in the outlet ducts, or alternatively may be respectively located in ram pipes which are connected one to each outlet duct.

United States Patent 1 1 1 1 ,814,069

Croft et al. June 4, 1974 [54] INLET MANIFOLDS 3,664,316 5/1972 Garcea 123/52 M [75] Inventors: Brian Hugh Croft, Coventry; Denis FOREIGN PATENTS QR APPLICATIONS Amhmy Brmnemorw'ch both of 421,011 5/1947 Italy 123/52 MF England v [73] Assignee: Joseph Lucas (Industries) Limited, P i E i -W d l] E, Burns Blrmlngh E g Attorney, Agent, or FirmBrisebois & Kruger [22] Filed: Dec. 28, 1971 211 Appl. 196.; 212,949 [571 ABSTRACT l An inlet manifold for a multi-cylinder internal com- [301 Foreign Applicafionpriority Data bustion engine comprises a plenumchamber. which Jan. 1, 1971 Great 13 1111111 142/71 has mm contammg at least one throttle Valve and which has a plurality of outlet ducts each adapted to [52] U S 123/52 M 123/] 19 R 123/139 Aw communicate with a respective cylinder of the engine 1 123/1212 123/52 via an inlet valve of the engme. A further valve is asso- [5l 1 lm Cl o 23/04 F02m 13/04 ciated with each outlet duct which, 1n use, operates to 58] Fie'ld 123/142 1 Aw 52 M control the flow of gas through that outlet duct under "i i 52 119 at least part of the yange of operation of the throttle valve which controls the operation of the engine. The 56] References Cited further valves may be respectively located in the outlet ducts, or alternatively may be respectively located UNITED STATES PATENTS in rain pipes which are connected one to each outlet 1,733,975 10/1929 Osterhout.... l23/l42 duct,

2,909,165 10/1959 D0122! 123/139 AW 3,167,059 1/1965- Love 123/52 MF 3 Cl'a'ir'ns',8Drawing Figures 5 ,10 L 1 I I60 60* .CQSNTTROL 5 EM 2 cs 9 @8 a l 11 l I I 1 I 1. l .l iil fin l a mfwif PATENTEDJUH M974 v sum 1 or 3 10 I com/:01 SYSTEM 1 MTENTEDJUN 41914 SHEET 3 BF 3 F ig.8 j

This invention relates to inlet manifolds for multicylinder internal combustion engines, particularly but not exclusively multi-cylinder internal combustion engines in which the fuel is injected into the inlet manifold just upstream of each inlet valve.

In high performance multi-cylinder internal combustion engines, there is normally a requirement that the inlet valve or valves in each cylinder should start to open before the exhaust valve or valves in the cylinder have fully closed. At low inlet manifold pressures, therefore, it is possible that exhaust gas may'flow into the inlet manifold, where it mixes with and dilutes the incoming charge. This reduces combustion efficiency,

The or each flap member may be made of rubber or plastics material, or may be made from metal, for example spring steel.

Where the engine is adapted to operate with fuel inj ectioninto the inlet manifold; each fuel injector may which in turn leads to increased exhaust emissions (i.e. I

of pollutants) and reduced engine stability.

According therefore to one aspect of the present invention, an inlet manifold for a multi-cylinder internal combustion engine comprises a plenum chamber which has an inlet containing at least one main throttle valve and which has a plurality of outlet ducts each adapted to be connected to a respective cylinder of the engine, each outlet duct containing, adjacent the downstream end thereof, a respective further valve which, in. use, offers a low flow resistance to gas flowing from the plenum chamber to the respective inlet valve of the engine but offers a high flow resistance to gas flowing towards the plenum chamber from the respective inlet valve of the engine, at least at low manifold pressures.

The main throttle valve. conveniently comprises a butterfly valve pivotally mounted in said inlet. 7

In one embodiment of the invention, each further valve comprises a respective further butterfly valve which is arranged to be slightly open when the main throttle valve is closed or substantially closed and which is arranged to open fully over the first small portion (e.g. one quarterlof the opening movement of the main throttle valve.

Thus each further valve may be mechanically connected to the main throttle valve, or may be connected to be opened by means responsive to manifold pressure or engine rotational speed.

In an alternative and preferred embodiment of the be mountedin a respective outlet duct of the inlet manifold either downstream of the check valve or, preferably, immediatelyupstream of the check valve.

According to another aspect of the present invention, an inlet manifold for a multi-cylinder internal combustion engine comprises a plurality of ram pipes each adapted to be connected to arespective cylinder of the engine, and a relatively small plenum chamber which .has an inlet containing a main throttle valve and which has a plurality of outlets each connected to a respective ram pipe adjacent the downstream end thereof, each ram pipe containing a respective secondary throttle valvev which is arranged to move, as the engine approaches full load operation, from a first position in which its ram pipe is substantially blocked and the outlet from the manifold to the ram pipe is substantially open to a second position in which its ram pipe is substantially openand the'outlet from the manifold to the ram pipe is substantially blocked.

Each secondary valve is' .preferably mechanically connected to the main throttle valve.

The upstream ends of the ram pipes may communicatc with a further,-relatively large, pleunm chamber which in turn communicates with the inlet containing the main throttle valve. Y

The invention also comprises a multi-cylinder inter nal combustion engine provided with an inlet manifold inaccordance with any of the preceding statements of invention.

The invention will now be described, by way of nonlimitative example only, with reference to the accompanying drawings, of which:

FIG. I is a diagrammatic representation of one embodiment of an inlet manifold in accordance with the present invention, fitted toa fuel-injected four cylinder internal combustionrengine for a road vehicle;

FIG. 2 is a diagrammatic representation of another embodiment of an inlet manifold in accordance with check valve.

Each check valve preferably comprises at least one movable flap member mounted in its respective outlet duct and movable, in response to the direction of the gas flow in the outlet duct. from a position in which the outlet duct is substantially blocked to a position in which the outlet ,duct is relatively unobstructed. Thus there may be two movable flap members substantially equiangularly disposed on opposite sides of the axis of the outlet duct andwhich are secured to the outlet duct adjacent their upstream ends. The respective upstream ends of the two flap members may be disposed on substantially opposite sides of the outlet duct in a plane FIGS. 3 and 4 are alternative forms of part of the inlet manifold of FIG. 2';

FIG. 5 shows one position for a fuel injection valve in the inlet manifold of FIG. 2; v

FIG. 6 is a diagrammatic representation of a yet further embodiment of an inlet manifold in acordance with the present invention, for use with the engine of FIG. 1;

FIG. 7 is asection on, the line 7-7 of FIG. 6; and FIG. 8 shows a modification of the embodiment of FIGS. 6 and .7.

The inlet manifold 10 of FIG; 1 comprises a plenum chamber 12 having an air inlet 14 which is connected to receive filtered air from. an airfllter (not shown) and which contains a main throttle butterfly valve 16 for controlling the amount of the air flowing into the ple num chamber 12. The position of the throttle valve 16 is in turn controlled by the driver of the vehicle. The plenum chamber 12 has four circularsection outlet ducts .18 in the form of tuned ram pipes, which comm unicate with the respectiveinlet valves of the four cylinders of the engine 20.

the'present invention, for use with the engine of FIG. v

Each duct l8contains a respective further butterfly valve 22 at or adjacent the downstream end thereof, i.e. just upstream of the respective inlet valve of the engine 20. Each of the butterfly valves 22 is mechanically connected-to the main throttle valve 16 by a linkage indicated diagrammatically at 24. The arrangement of the linkage 24 is such that when the main throttle valve ,16 is closed or substantially closed, each butterfly valve 22 is slightly open, and when the main throttle valve 16 starts to open, each butterfly valve 22 opens fully over the first few degrees of movement of the main throttle valve 16.

The engine is provided with a fuel injection system which includes four electromagnetically operable fuel injection valves 26 which are positioned, one in each outlet duct 18, immediately downstream of the respective butterfly valve 22. The fuel injection valves 26,

which may for example bedescribed in United Kingdom Pat. No. 1,064,679, are connected to be supplied with fuel at substantially constant pressure, for example as described in United Kingdom Pat. No. 1,038,541. The timing and duration of the opening periods of the fuel injection valves 26, and hence the quantity of fuel supplied to the engine, are controlled in dependence upon engine operating parameters such as inlet manifold pressure, rotational speed and coolant temperature by an electronic control system 28, which may be as described in United Kingdom Patent. No.1,107,989. The electronic control system 28 is connected to receive as a controlsignal, inter alia, a signal which is indicative of inlet manifold pressure and which is' produced by a pressure transducer 29 connected to the plenum chamber 12.

In operation, the valve timing of the engine 20 is such that there is valve overlap, i.e. the inlet valve on each cylinder starts to open before the exhaust valve on the cylinder has fully closed. Thus when the engine20 is idling, i.e. the main throttle valve 16 is closed or substantially closed, the pressure in the inlet manifold 10 is relatively low and there is a tendency for the exhaust gas in each cylinder to flow back into its respective outlet duct 18 during the valve'overlap period. However, the butterfly valves 22 are only slightly open, the amount of the opening being chosen to offer a low flow resistance to the small relatively steady flow of idling air. towards the engine but a high flow resistance to the short, fast puffs of exhaust gas trying to flow back through the inlet valves. The amount of exhaust gas which enters the inlet manifold 10 to dilute the incoming charge is thus substantially reduced, which in turn improves combustion efficiency and engine stability and reduces exhaust emissions.

At engine speeds substantially above idling, e.g. speeds above 15002000 R.P.M., the pressure in the inlet manifold 10 increases, and the problem is not so severe: the butterfly valves 22 are therefore arranged to open fully over the first few degrees, e.g; overthe first quarter, of angular movement of the main throttle valve 16. v

The embodiment of the invention shown in FIG. 2 is very similar to the embodiment of- FIG. 1, so in the description which follows the same reference numerals willbe used where appropriate and only thepoints of difference will be described. Thus in thelrFIG'. '2 embodiment of the invention, the butterfly valves 22 and their associated linkage 24 of the FIG. 1 embodiment are replaced by respective automatic check valves 30 4 mounted in each ,outlet duct 18 adjacent the downstream end thereof.

The check valves 30 shown in FIG. 2 are each moulded in'on'e piece from a suitably temperature resistant natural or syntheticrubber and each comprise an annular portion 32 which is bonded or otherwise suitably secured to theinternal surface of its respective outlet duct 18. Two "converging flap members 34 are substantially equiangularly disposed on opposite sides of the axis of the outlet duct 18 andextend in a downstream direction from diametrically opposed parts of the annular portion 32. The fl'aprnembers 34 are. joined together at their sides so as to form a tapering nozzle terminating in a slit-like aperture36 almostequal in width to the diameter of the outlet duct 18.

In operation, the check valves 30 offer a very low flow resistance to gas flowing through the outlet ducts 18 towards the inlet valves of the engine 20, since the flexibility of the rubber flap members 34 permits them to separate in response to the pressure exerted on their internal surfaces by the How, so distorting the 'slit-like aperture 36 to a relatively largeapproximately circular shape;'However, gas flow in the opposite direction i.e. from theinlet valves of the engine 20,-is strongly resisted, since it acts-on the external surfaces of the rubber flap members 34 to urge them'into contact with each other, so substantially closing the slit-like aperture 36 and blocking the outlet duct 18. The check valves 30 thus affect exhaust emissions and engine stability in a manner similar to that described with reference to FIG. '1, but are more effective than the valves 22, over a wider range of pressures in the inlet manifold 10, by virtue of the factthat they substantially completely block 'the' reverse flow of exhaust gases into the inlet manifold 10. I

An alternative form for the checkvalves 30, suitable for usewhen the outlet ducts l8 aresubstantially rectangular in cross-section, is shown in FIG. 3, and comprises a pair of substantially rectangular flap members 40 which are'substantially equal in width to the width of their outlet duct 18 and made of spring steel or plastics material such as that available under the trade name-TUFNOL (Registered Trade Mark). The flap members 40'are substantially equiangularly disposed on opposite sides of the axis'of the outlet duct 18 and converge in a downstream direction, and their upstream ends. 42 are flexibly secured in respective rubber blocks 44 bonded to opposite sides of the outletduct 18: it will be appreciated, however, that if the flap members 40 are sufficiently flexible-their ends 42 may be directly secured to opposite walls ofthe outlet duct 18 and the rubber blocks 44 maybe omitted.

In operation, the flap members 40 are easily urged apart so as to open their respective outlet ducts 18 in response to gas flow towardsthe inlet valve of the engine 20, but are urged into contact with each other so i as to substantially close their respective outlet. duct 18 flap members 40 of FIG. 3 but whose upstream ends 52 I are 'flexibly secured in a common rubber block 54 which extends across'the middle of the outlet duct 18 normal to the axis thereof. The flap members 50 are still substantially equiangularly disposed on opposite sides of the axis of the outlet duct 18, but diverge in a downstream direction. In this embodiment, the flap members 50 are easily urged towards each other in the centre of the outlet duct 18, so as to open it, by gas flowing towards the inlet valve, but are respectively urged into contact with opposite sides of the outlet duct 18, so as to substantially close it, by gas flowing from the inlet valve.

If desired, the block 54 can be replaced by a pivot pin (not shown) to which each flap member 50 is pivotally secured, the flap members 50 then being urged apart by a light torsion spring. Alternatively, if the flap members 50 are sufficiently flexible, their upstream ends 52 may be directly secured to a transverse pin normal to the axis of the outlet duct 18. a

In general the flap members 40 and 50 of FIGS. 3 and 4 may be relatively flexible and rigidly secured, or relatively stiff and flexibly secured, or relatively flexible and flexibly secured, within the outlet duct 18.

In the embodiments of the invention described with reference to FIGS. 2, 3 and 4, the fuel injection valves 26 are shown positioned immediately downstream of their respective check valves 30. However, in these embodiments, particularly the FIG. 3 embodiment, it may be advantageous to position the fuel injection valves 26 just upstream of their respective check valves 30 as shown in FIG. 5. lnthis case, the timing of the instant of opening of each injection valve 26 becomes less significant (as long as it is before the instant that air starts to flow through the respective check valves 30), since the injected fuel will collect on the upstream side of the check valves 30, between the flaps 34, 40 or 50, until the check valves 30 open. Further, the flow of air past the flaps 34, 40 or 50 when the check valves 30 open tend to cause them to vibrate rapidly, which vibration assists good atomisation of the fuel.

Referring now to FIGS. 6 and 7, the inlet manifold 10 shown therein comprises four tuned ram pipes 60 each communicating with a respective inlet valve of the four cylinders of the engine 20. The upstream ends of the ram pipes 60 are open to atmospheric pressure. The ram pipes 60 are joined together by a relatively small plenumchamber or balance pipe 62 which has an air inlet 64 containing a main throttle butterfly valve 66 and which has four outlets 68 each connected to a respective one of the ram pipes 60 adjacent the downstream end thereof. The inlet 64 is connected to receive filtered'air from an air filter (not shown).

Each ram pipe 60 contains, adjacent the respective outlet 68, a respective further valve 70 which is connected to the main throttle valve 66 by a linkage indicated diagrammatically at 72. The arrangement of the linkage 72 is such that as the main throttle valve 66 approaches its fully open position, e.g. when the engine is operating at about 90 percent of its full load, each of the valves 70 moves from a first position in which it substantially blocks the ram pipe 60 and opens the outlet 68 to a second position in which it substantially blocks the outlet 68 and opens the ram pipe 60. Thus at part engine loads, air is supplied to the engine via the main throttle valve 66 and the small plenum chamber 62, while at full load air is supplied to the engine 20 directly via the ram pipes 60.

The engine 20 is provided with a fuel injection system substantially identical to that described with reference to FIG. 1, the fuel injection valves 26 being positioned in the ram pipes 60 immediately downstream of the outlets 68, and the pressure transducer 29 being connected to the small plenum chamber 62.

Since the volume of the plenum chamber 62 is rela' tively small, the tendency of the exhaust gas to flow back into it during the valve overlap period, at part engine loads, is reduced, which leads to the reduced exhaust emissions and improved engine stability already mentioned. At full engine load, however, the plenum chamber 62 would restrict the amount of air entering the engine 20, whereas the ram pipes 60 offer little restriction and permit full engine power to be developed readily.

Theupstream ends of the ram pipes 60 can each be provided with respective coarse filters (not shown) to prevent the ingress of small stones and similar debris. Alternatively, as shown in FIG. 8 they may all be connected to a further, relatively large plenum chamber 74 incorporating an air filter and silencer (not shown) arranged in parallel with the plenum chamber 62: in this case the inlet 64 would be enlarged and would serve as the inlet for both plenum chambers.

It will be appreciated that many modifications may be made to the described embodiments of the invention. For example, the check valves 30 of FIGS. 3 and 4 could readily be adpated for use in circular-section ducts, while the butterfly valves 22 of FIG. 1 and the check valves 30 of FIG. 2 would readily be adapted for use in rectangular-section ducts. Also, both the linkage 24 of FIG. land the linkage 72 of FIGS. 6 and 7 could be replaced by a suitable automatic device which operates the respective valves 22 or in response to e.g. a predetermined manifold pressure or range of manifold pressures, or a predetermined engine rotational speed or range of rotational speeds. Moreover, if desired more than one main throttle butterfly valve 16 (or 66) may be provided. Finally, the inlet manifolds of the present-invention are not only applicable to fuel injected engines: they can be modified for use with multicylinder internal combustion engines having one or more carburettors.

We claim:

1. An inlet manifold for a multi-cylinder internal combustion engine comprising aplurality of ram pipes each-adapted to be connected to a respective cylinder of the engine,and a relatively small plenum chamber which has an inlet containing a throttle valve and which has a plurality of outlets each connected to a respective ram pipe adjacent the downstream end thereof, each ram pipe containing a further valve which is arranged to move, as the engine approaches full load operation, from a first position in which its ram pipe is substantially blocked and the outlet from the plenum chamber to the ram pipe is substantially open to a second position in which its ram pipe is substantially open and the outlet from the plenum chamber to the ram pipe is substantially blocked.

2. An inlet manifold as claimed in claim 1, wherein the upstream ends of the ram pipes communicate with a further, relatively large, plenum chamber which in turn communicates with said inlet containing the throttle valve.

3. An inlet manifold as claimed in claim 1, for use with an engine adapted to operate with fuel injection into the inlet manifold, wherein a fuel injector is mounted in each outlet duct of the inlet manifold downstream of the further valve. 

1. An inlet manifold for a multi-cylinder internal combustion engine comprising a plurality of ram pipes each adapted to be connected to a respective cylinder of the engine, and a relatively small plenum chamber which has an inlet containing a throttle valve and which has a plurality of outlets each connected to a respective ram pipe adjacent the downstream end thereof, each ram pipe containing a further valve which is arranged to move, as the engine approaches full load operation, from a first position in which its ram pipe is substantially blocked and the outlet from the plenum chamber to the ram pipe is substantially open to a second position in which its ram pipe is substantially open and the outlet from the plenum chamber to the ram pipe is substantially blocked.
 2. An inlet manifold as claimed in claim 1, wherein the upstream ends of the ram pipes communicate with a further, relatively large, plenum chamber which in turn communicates with said inlet containing the throttle valve.
 3. An inlet manifold as claimed in claim 1, for use with an engine adapted to operate with fuel injection into the inlet manifold, wherein a fuel injector is mounted in each outlet duct of the inlet manifold downstream of the further valve. 